Recovery of the ventilatory response to hypoxia in normal adults.

Recovery of the initial ventilatory response to hypoxia was examined after the ventilatory response had declined during sustained hypoxia. Normal young adults were exposed to two consecutive 25-min periods of sustained isocapnic hypoxia (80% O2 saturation in arterial blood), separated by varying interludes of room air breathing or an increased inspired O2 fraction (FIO2). The decline in the hypoxic ventilatory response during the 1st 25 min of hypoxia was not restored after a 7-min interlude of room air breathing; inspired ventilation (VI) at the end of the first hypoxic period was not different from VI at the beginning and end of the second hypoxic period.

Ventilatory response to sustained hypoxia in normal adults.

We examined the ventilatory response to moderate (arterial O2 saturation 80%), sustained, isocapnic hypoxia in 20 young adults. During 25 min of hypoxia, inspiratory minute ventilation (VI) showed an initial brisk increase but then declined to a level intermediate between the initial increase and resting room air VI. The intermediate level of VI was a plateau that did not change significantly when hypoxia was extended up to 1 h.

Effects of hydralazine and nitroprusside on cardiopulmonary function when a decrease in cardiac output complicates a short-term increase in pulmonary vascular resistance.

We investigated the short-term cardiopulmonary effects of nitroprusside and hydralazine when cardiac output (CO) was reduced by a short-term increase in pulmonary vascular resistance (PVR). In six anesthetized, ventilated dogs, small autologous blood clots, injected over 1 to 2 hr, increased right ventricular afterload. When CO had fallen approximately 40%, dogs were treated with nitroprusside and subsequently with hydralazine.

Treatment of canine low pressure pulmonary edema. Nitroprusside versus hydralazine.

In canine oleic acid pulmonary edema, we investigated acute cardiopulmonary effects of different doses of nitroprusside and compared the results with those obtained after intravenously administered hydralazine. Oleic acid increased (p less than 0.05) intrapulmonary shunt (Qs/Qt), increased (p less than 0.

Effect of previous volume history on airway closure.

We studied the effect of volume history on airway closure in six healthy males ranging from 32 to 67 yr of age. The method used was to compare the regional distribution of 133Xe boluses distributed according to N2O uptake during open-glottis breath-hold maneuvers with the regional distribution of boluses of intravenously injected 133Xe. Measurements were made at two lung volumes, one close to residual volume (RV) and the other just below closing volume.